1. Field of the Invention
The present invention relates to a container cover. In particular, it relates to a cover for a container of a truck having a material carrying container, such as a tipper truck.
2. Description of the Prior Art
It is well known to provide a cover for the material carrying container of a truck. Such covers are particularly useful when transporting loose materials such as sand or gravel, to prevent the load from being blown out of the container by the wind. Additionally, the cover protects the load from contamination. Many examples of container covers are known in the prior art. A popular arrangement for covering a truck container is to use a tarpaulin (or xe2x80x98tarpxe2x80x99) or other flexible cover, mounted upon a roller assembly adjacent one end of the truck container. The tarp is pulled from one end of the truck to the other by means of a front-to-rear pivot arm assembly.
Typically in such arrangements, a roller bar and bearing assembly is permanently mounted to the front of the truck, usually upon the headboard or cab shield of the vehicle. The roller bar assembly includes a set of bearings mounted upon bearing plates or a tarp housing assembly that includes a wind deflector spanning the entire width of the vehicle body. If bearing plates are used instead of a tarp housing, a separate wind deflector may be mounted between the bearing plates to prevent the wind from blowing under the tarp when the pivot arms are in the deployed position. Such arrangements are not without problems.
If the permanently mounted roller assembly is positioned low down on the headboard or cab shield (such as that shown in U.S. Pat. No. 5,275,459), the tarp covers the container body most effectively, with no gap along the sides and thus most effectively protected from the wind. However, the roller bar is then susceptible to damage from material being loaded into the container, or from loading apparatus striking the roller assembly which is mounted at or near the level of the container opening.
To prevent such damage, the permanently mounted roller bar assembly is often mounted higher up on the headboard or cab shield (see for example U.S. Pat. Nos. 5,031,955 and 5,957,523), the tarp and assembly is most effectively out of the way of the loading apparatus and material being loaded and is thus well protected from damage. However, the tarp, when in the deployed position, is spaced from the upper edge of the container at the front and sides of the vehicle and is thus highly susceptible to wind entering under the tarp during transit, inflating the tarp. This has several disadvantageous results. Firstly, the increased air resistance creates greater drag on the vehicle and increases fuel consumption. Secondly, the gap that is created in the side of the tarp above the side rails of the container allows the wind to blow the contents of the container around and, escape through the side gap in the tarp. The life of the tarp itself is often reduced as well because of excessive and continual flapping from the wind. Thus the effectiveness of the cover is dramatically reduced.
Several solutions to these apparent problems have been devised. U.S. Pat. No. 5,031,955, describes the use of a secondary arm attached to the pivot arm and adapted to exert a downward force upon the tarp adjacent the forward edge of the container body. U.S. Pat. No. 5,957,523 describes a similar arrangement in which a secondary arm mounted upon the headboard or cab shield is used to exert a downward force upon the tarp adjacent the front of the container. In both cases, the roller assembly is mounted at the top of the headboard or cab shield. Such an arrangement still presents the leading edge of the tarp to the wind, thus still acting to funnel wind under the tarp, albeit at a reduced level if used in conjunction with a mesh or net tarp. These configurations are not effective with a tarp made of solid, non-mesh material such as a solid vinyl tarp unless great force is exerted in a downward direction on the tarp from the secondary arm mechanism to lock the arm in place. If great force is not used to hold down the tarp, a parachute effect will overcome the vertical portion of the solid tarp and lift the secondary arm up, rendering it useless in performing its function to hold down the tarp in the front of the container opening. Increased fuel consumption remains a problem in that increased air resistance is created by the vertical portion of the tarp between the roller assembly mounted at the top of the headboard or cab shield and the top side edges of the container.
The present invention has been devised in order to address the deficiencies in the prior art.
According to the present invention in one aspect there is provided a cover assembly for a container of a vehicle; the container having first and second ends and the cover assembly comprising a retractable cover having a first end attached to a roller assembly and a second end attached to a cover support element, the cover assembly comprising rolling means adapted to roll the cover upon the roller assembly. The cover support element is supported by at least one pivot arm at an upper end thereof, said pivot arm being pivotable about a lower end thereof at a point intermediate the two ends of the container and adjacent the bottom of the container, between a first position in which the cover support element is adjacent the first end of the container and a second position in which the cover support element is adjacent the second end of the container. The roller assembly is mounted for movement between a lower position in which the roller assembly is substantially adjacent the top of the container at the first end thereof when the pivot arm is in said second position, and an upper position in which the roller assembly is more greatly spaced from the top of the container when the pivot arm is in the first position.
Preferably, said rolling means comprises a motor assembly associated with the roller assembly. Typically, the motor assembly is an electric, pneumatic or hydraulic motor. The motor assembly may be mounted externally from the roller assembly. Alternatively, the roller assembly includes a cavity adapted to house the motor assembly. Alternatively or additionally, the rolling means includes a spring assembly adapted to bias the retractable cover into a rolled configuration.
Preferably, the at least one pivot arm is biased by means of a spring associated with the lower end of the pivot arm into a position in which the cover support element is adjacent the second end of the container. Alternatively, the at least one pivot arm is biased by means of hydraulic or pneumatic cylinder(s) in conjunction with a spring biased roller assembly.
In one embodiment, the roller assembly is mounted for movement between the upper and lower positions by being mounted upon at least one pivotally mounted roller arm. More preferably, the roller arm is pivotally mounted at a point intermediate the upper and lower positions. Typically, the vehicle is a road lorry having a headboard or cab-shield and the roller arm pivot point is provided internally or externally mounted on the side plates of the headboard or cab-shield, or upon a rearwardly directed sidewall attached to the headboard or cab-shield.
In a further embodiment, in which the vehicle or the container is provided with sidewalls adjacent and above each side of the first end of the container, the roller assembly is mounted for movement between upper and lower positions by being mounted to run between and in respective tracks formed in the sidewalls. In one arrangement, the tracks are non-linear and may be arcuate, conforming to the shape and design of the headboard or cab shield. In an alternative arrangement, the tracks are linear.
In a yet further embodiment, each roller arm is pivotally mounted upon a respective pivot arm.
Advantageously, the roller assembly further includes a tie bar substantially parallel with the roller bar and extending below the roller bar to contact the top edges of the container side rails when the tarp is in the fully extended position. Thereby the roller bar and tarp are prevented from contacting the top side edges or any other part of the container while the tarp is rolled onto or off of the roller bar. The tie bar also acts as a stabilizer bar that allows the two roller arms and the roller assembly to move synchronously between the fully retracted and fully extended positions.
It can be considered that a single actuating means works in conjunction with a spring force to move pivot arms between the first and second positions and move the roller assembly between the lower and upper positions.
In another aspect, the present invention provides a covering assembly for covering a open top of a vehicle mounted container having a first end and a second end joined by two side walls, together forming an upper edge that defines the container opening. The cover assembly further comprises a retractable cover having a first end attached to a variable position roller assembly, and a second end attached to a cover support element. The cover support element extends substantially transversely between the two side walls of the container and is supported by at least one pivot arm attached to the end of the cover support element at the upper end of the at least one pivot arm. The at least one pivot arm is pivotable about a lower end thereof at a point (in one embodiment) on or adjacent at least one of the two side walls, intermediate the first and second ends of the container, and is biased about the intermediate point between a first position in which the cover support element is adjacent the first end of the container and a second position in which the cover support element is adjacent the second end of said container. The variable position roller assembly is mounted with means for movement of the roller assembly from a first position in which the roller assembly is substantially adjacent or below the upper edge of the first end of the container when the at least one pivot is in the second position. The roller assembly moves through a variable range of motion as the at least one pivot arm moves to a first position in which the roller assembly substantially meets the cover support element at the first position of the at least one pivot arm, adjacent the first end of the container. The roller assembly is actuated by rolling means.
Suitably, the biasing means to move at least one pivot arm from said first position to said second position is a torsion, compression, or extension spring. Alternatively, the biasing means comprises at least one hydraulic or pneumatic cylinder, or electric motor-driven actuator.
Preferably the first position of the variable position roller assembly is a lower position in which the roller assembly is substantially adjacent the upper edge of the container at the first end thereof when the at least one pivot arm is in the second position, and the second position is an upper position in which the roller assembly is more greatly spaced from the upper edge of the container when the at least one pivot arm is in the first position.
In one embodiment, preferably, the means for movement of the roller assembly includes at least one pivotally mounted roller arm, pivotally mounted at a point intermediate the upper and lower positions. Typically, the rolling means is an electric, pneumatic, or hydraulic motor associated with the roller assembly Advantageously, the rolling means includes a spring assembly adapted to bias the retractable cover into a rolled configuration.
In a second embodiment, the rolling means is a manual crank assembly including chains and sprockets and/or belts and pulleys to bias the roller assembly.
Suitably, the means for movement of the roller assembly includes at least one pivotally mounted roller arm supporting at least one end of the roller assembly.
Alternatively, the means for movement of the roller assembly includes a track system in which both ends of the roller assembly are supported by and slide within parallel tracks mounted on or from the container.
Suitably, the roller assembly is actuated by a rolling means which in turn actuates the movement of the roller assembly throughout its variable range of motion in cooperation with the movement of the at least one pivot arm between the first and second positions.
In an alternative embodiment, the at least one pivot arm is pivotally mounted to a frame of the vehicle.
Equally, in an alternative embodiment, the variable position roller assembly is also mounted to the frame of the vehicle.
It will be appreciated by those skilled in the art that reversing the positions of the cover support element and the variable position roller assembly will obtain the same objectives. Accordingly, these arrangements form a yet further aspect of the present invention.